Fractional Excretion of Sodium (FENa) — free guideline decision tool
Calculate the fractional excretion of sodium (FENa) to work up acute kidney injury.
Open guideline tool →Guideline-based
Implements the decision logic from published clinical guidelines.
Runs in your browser
No installation. Enter the patient's values and get a guideline recommendation instantly.
Data stays local
Nothing is uploaded. Results are for licensed clinicians only.
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Urine sodium | 20 mmol/L |
|---|---|
| Plasma sodium | 140 mmol/L |
| Urine creatinine | 100 mg/dL |
| Plasma creatinine | 2.0 mg/dL |
→FENa0.29%
- Interpretation：< 1% — suggests pre-renal
- Formula：FENa = (UNa·PCr)/(PNa·UCr) × 100
Common questions
What is Fractional Excretion of Sodium (FENa)?
Calculate the fractional excretion of sodium (FENa) to work up acute kidney injury.
How is Fractional Excretion of Sodium (FENa) calculated? What is the core formula?
FENa = (UNa × PCr) / (PNa × UCr) × 100. < 1% pre-renal; > 2% intrinsic/ATN.
When is Fractional Excretion of Sodium (FENa) used?
Differentiate pre-renal from intrinsic (ATN) acute kidney injury.
What are the key clinical points for Fractional Excretion of Sodium (FENa)?
Unreliable after diuretics — use FEUrea instead. Also unreliable in CKD, contrast nephropathy and glomerulonephritis. Interpret with the clinical picture and urine microscopy.
What are the limits and cautions when using Fractional Excretion of Sodium (FENa)?
For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
How is Fractional Excretion of Sodium (FENa) calculated in practice? Can you show a worked example?
Inputs: Urine sodium 20 mmol/L, Plasma sodium 140 mmol/L, Urine creatinine 100 mg/dL, Plasma creatinine 2.0 mg/dL → Result: FENa 0.29 %（Interpretation: < 1% — suggests pre-renal, Formula: FENa = (UNa·PCr)/(PNa·UCr) × 100）
Run Fractional Excretion of Sodium (FENa) now
Calculate the fractional excretion of sodium (FENa) to work up acute kidney injury.
Open guideline tool →For licensed clinicians. Not a substitute for clinical judgement.
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